In recent, as the interest on electric or hybrid vehicles not using fossil energy but using electric energy due to exhaustion of fossil fuels and environmental pollution is increased, the study on electric or hybrid vehicles is actively progressed. An electric or hybrid vehicle needs electric energy to drive a motor used for the vehicle, and the electric energy should be supplied by means of a battery.
A battery used for the electric or hybrid vehicle generally adopts a secondary battery, which may repeat a discharging process for converting chemical energy into electric energy and a charging process for converting electric energy into chemical energy. Such a secondary battery includes a nickel-cadmium battery, a nickel-hydrogen battery, a lithium ion battery, and a lithium ion polymer battery. Such secondary batteries are classified into lithium-based batteries and nickel-hydrogen-based batteries. The lithium-based batteries are mainly used for small products such as digital camera, P-DVD, MP3P, cellular phone, PDA, portable game device, power tool and E-bike, while the nickel-hydrogen-based batteries are mainly applied to and used for large products such as electric or hydride vehicles, which require high output.
Meanwhile, in case a battery is used as a power source, the battery should keep good insulation against external devices except for a battery management system. If the insulation of the battery is not kept, there occurs leakage current. If leakage current occurs, it can be primarily a factor of discharge of the battery and malfunction or breakdown of electronic equipment to which the battery is applied. In particular, if leakage current occurs in a high voltage battery in for example an electric or hybrid vehicle, the leaked current may fatally shock a person. Accordingly, in the related art, it is urgent to develop a scheme to thoroughly sense leakage current of a battery.